Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H, W = map(int, input().split())
edges = [0] * (W + 2)
field = [edges]
WH = 0
for _ in range(H):
    row = [c == '.' for c in input()]
    field.append([0] + row + [0])
    WH += sum(row)
field.append(edges)
que = deque([(1, 1, 1)])  # x, y, cnt
enq, deq = que.append, que.popleft
while que:
    x, y, cnt = deq()
    if (x, y) == (W, H):
        print(WH - cnt)
        exit()
    for dx, dy in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        nx, ny = x + dx, y + dy
        if field[ny][nx]:
            enq((nx, ny, cnt + 1))
            field[ny][nx] = 0
print(-1)